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<h1>Writing Clang Tools</h1>
<p>Clang provides infrastructure to write tools that need syntactic and semantic
information about a program. This document will give a short introduction of the
different ways to write clang tools, and their pros and cons.</p>

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<h2 id="libclang"><a href="http://clang.llvm.org/doxygen/group__CINDEX.html">LibClang</a></h2>
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<p>LibClang is a stable high level C interface to clang. When in doubt LibClang
is probably the interface you want to use. Consider the other interfaces only
when you have a good reason not to use LibClang.</p>
<p>Canonical examples of when to use LibClang:</p>
<ul>
  <li>Xcode</li>
  <li>Clang Python Bindings</li>
</ul>
<p>Use LibClang when you...</p>
<ul>
  <li>want to interface with clang from other languages than C++</li>
  <li>need a stable interface that takes care to be backwards compatible</li>
  <li>want powerful high-level abstractions, like iterating through an AST
with a cursor, and don't want to learn all the nitty gritty details of Clang's 
AST.</li>
</ul>
<p>Do not use LibClang when you...</p>
<ul>
  <li>want full control over the Clang AST</li>
</ul>

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<h2 id="clang-plugins"><a href="ClangPlugins.html">Clang Plugins</a></h2>
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<p>Clang Plugins allow you to run additional actions on the AST as part of
a compilation. Plugins are dynamic libraries that are loaded at runtime by
the compiler, and they're easy to integrate into your build environment.</p>
<p>Canonical examples of when to use Clang Plugins:</p>
<ul>
  <li>special lint-style warnings or errors for your project</li>
  <li>creating additional build artifacts from a single compile step</li>
</ul>
<p>Use Clang Plugins when you...</p>
<ul>
  <li>need your tool to rerun if any of the dependencies change</li>
  <li>want your tool to make or break a build</li>
  <li>need full control over the Clang AST</li>
</ul>
<p>Do not use Clang Plugins when you...</p>
<ul>
  <li>want to run tools outside of your build environment</li>
  <li>want full control on how Clang is set up, including mapping of in-memory
  virtual files</li>
  <li>need to run over a specific subset of files in your project which is not
  necessarily related to any changes which would trigger rebuilds</li>
</ul>

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<h2 id="libtooling"><a href="LibTooling.html">LibTooling</a></h2>
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<p>LibTooling is a C++ interface aimed at writing standalone tools, as well as
integrating into services that run clang tools.</p>
<p>Canonical examples of when to use LibTooling:</p>
<ul>
  <li>a simple syntax checker</li>
  <li>refactoring tools</li>
</ul>
<p>Use LibTooling when you...</p>
<ul>
  <li>want to run tools over a single file, or a specific subset of files,
  independently of the build system</li>
  <li>want full control over the Clang AST</li>
  <li>want to share code with Clang Plugins</li>
</ul>
<p>Do not use LibTooling when you...</p>
<ul>
  <li>want to run as part of the build triggered by dependency changes</li>
  <li>want a stable interface so you don't need to change your code when the
  AST API changes</li>
  <li>want high level abstractions like cursors and code completion out of the
  box</li>
  <li>do not want to write your tools in C++</li>
</ul>

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<h2 id="clang-tools"><a href="ClangTools.html">Clang Tools</a></h2>
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<p>These are a collection of specific developer tools built on top of the
LibTooling infrastructure as part of the Clang project. They are targeted at
automating and improving core development activities of C/C++ developers.</p>
<p>Examples of tools we are building or planning as part of the Clang
project:</p>
<ul>
  <li>Syntax checking (clang-check)</li>
  <li>Automatic fixing of compile errors (clangc-fixit)</li>
  <li>Automatic code formatting</li>
  <li>Migration tools for new features in new language standards</li>
  <li>Core refactoring tools</li>
</ul>

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